350 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
mushroom-like Cop-inus stercorarms, when grown mider normal 
conditions so that it easily emerges into daylight, has a well- 
formed cap (y ileus) and a short stalk which increases in length 
as the spores ripen. But if the Coprinus is grown in darkness 
hardly any caps are formed, and those which are developed 
remain dwarfed ; while the stalk, on - the contrary, grows 
enormously, even to as much as two feet in length. This 
corresponds precisely to the etiolation form of a bean or a 
potato, the dwarf caps of the Coprinus representing the un- 
developed leaves, and the overgrown stalk the exaggerated inter- 
nodal development. How the case of Coprinus is explained on 
the nutrition theory I do not know, but from the point of view 
of adaptation it is easy to understand. The function of the 
stalk and pileus is to scatter the spores, and daylight serves to 
signal to the plant that it has reached the outer world, where 
its spores will have a chance of being distributed. Until this 
signal is given, the whole energy of growth is thrown into the 
lengthening of the stalk, while the production of spores is in 
abeyance. Brefeld says that the enormously etiolated stalks 
cease to grow in length, and develop caps and spores as soon 
as they are exposed to light. The same sort of thing may 
be seen in flowering plants ; a Narcissus grown in darkness 
makes an enormously elongated scape — a despairing effort to 
reach the outer world where it may receive and distribute pollen. 
Again, the etiolated Crocus produces under like conditions a 
flower-tube of exaggerated length. The remarkable fact that 
the flowers of many species are checked in development by dark- 
ness * may possibly belong to the same category. 
We must now return to the main problem. Assuming that 
etiolation is a case of adaptive response to signals or stimuli, 
how far do the fundamental facts support such a view ? The 
growth of the leaves of such plants as the cereals, of Crocus, and 
of Hyacinth, entirely accords with Godlewski's theory. The only 
way in which they can escape from darkness into light is by their 
own growth ; there is no elongation of stem to carry them out, 
so that if they were dwarfed by darkness they never could escape 
into daylight. Another point in their manner of growth points 
to the same conclusion : they are not only abnormally long, but 
* Vocliting, I ringsJicivi's Jain biicJicr, Bd. xxv. 18!).'5. 
